Description

This keeps writing to the old schema as well, so we can still easily back out of the migration.

NOTE: we'll want to have this enabled on the live systems for a while before releasing it as the default for 3rd party installs with MW-1.32-release. But we'll want to have this as the default on master / for CI before enabling it on the live systems, see T198561.

NOTE:This enables the usage of extra slots on the live systems!
If we are forced to roll this back, we will lose access to the content of the new, extra slots. Rolling forward again would restore that access for old revisions, but extra cleanup would be needed to then again associate that content with newer revisions, made while the change was rolled back. Users should avoid large-scale edits that would be broken by a rollback until we're reasonably sure a rollback isn't going to be needed.

This task is currently blocked on some bugfixes. If it gets unblocked during the datacenter switchover (Sept 12 - Oct 12, I believe) we need to sync with the DBAs beforehand to be sure they have capacity to keep an eye out for DB overload in the read-new queries (and/or that the changed queries won't screw up other measurements they're trying to do).

Note: @jcrespo asked us to hold off on deploying to wikidatawiki until the s8 data issue is completely fixed. He requests we ping him whenever we're ready to do that wiki. He estimates it should be done by tomorrow or at the very latest next week, which should be fine since we're not planning further deployments here until after TechConf.

Note: @jcrespo asked us to hold off on deploying to wikidatawiki until the s8 data issue is completely fixed. He requests we ping him whenever we're ready to do that wiki. He estimates it should be done by tomorrow or at the very latest next week, which should be fine since we're not planning further deployments here until after TechConf.